Vitamin E is an antioxidant that is essential for development of the nervous system. The term “Vitamin E” encompasses many classes of chemicals, and the type of Vitamin E best absorbed by humans is alpha-tocopherol. Eight distinct stereoisomers of alpha tocopherol exist, but the only form of alpha-tocopherol found in nature is RRR-alpha-tocopherol. In comparison, synthetic alpha-tocopherol is made of essentially equal amounts of all eight stereoisomers.
It is known that the stereoisomers of alpha-tocopherol differ in their bioavailability, with RRR-alpha-tocopherol being the most bioavailable form. It is also known that, in certain species (e.g., rat), the brain also preferably selects and absorbs RRR-alpha-tocopherol as compared to the seven other stereoisomers.